As LSI circuits are increasing in density, circuit linewidths of semiconductor devices are becoming finer year by year. To form a desired circuit pattern on a semiconductor device, a method is used which includes reducing the size of a high-accuracy original pattern (mask or also called a reticle which is used, in particular, in a stepper or a scanner) formed on quartz and transferring the pattern to a wafer with a reduced projection exposure apparatus. The high-accuracy original pattern is written through an electron beam writing apparatus by means of so-called electron beam lithography technology.
Known electron beam writing apparatuses include a multi-beam writing apparatus that performs multi-beam irradiation, or irradiation with multiple beams at one time to improve throughput. In such a multi-beam writing apparatus, for example, an electron beam emitted from an electron gun passes through an aperture member having a plurality of holes, thus forming multiple beams. Each of the beams is blanking-controlled in a blanking plate. The beams which have not been blocked are reduced in size by an optical system and are then applied at desired positions on a mask, serving as a writing target.
For electron beam writing with the multi-beam writing apparatus, the layout of a semiconductor integrated circuit is designed and design data is generated as layout data. A polygonal figure included in the design data is divided into a plurality of trapezoids, thus generating write data to be input to the multi-beam writing apparatus. The write data includes, for each trapezoid, coordinate data indicative of a placement origin corresponding to one vertex of the trapezoid and data indicative of displacements from the placement origin to the other three vertices of the trapezoid.
If design data includes a figure, such as an oval figure, approximately represented with a polygonal figure having many sides, the polygonal figure will be divided into many trapezoids, resulting in an enormous amount of write data which includes, for each of the many trapezoids, coordinate data indicative of a placement origin and data indicative of displacements from the placement origin to the other three vertices.
The amount of the write data can be reduced by representing the polygonal figure with polygons. If such write data is input to the multi-beam writing apparatus, however, the amount of calculation necessary for data processing, such as rasterization, in the apparatus will increase.